This invention relates to a method to reduce formation of a coke material on a Transfer Line Exchanger (TLE exchanger) tubesheet by injecting steam into a hydrocarbon effluent from a hydrocarbon cracking furnace. This invention particularly relates to an apparatus for injecting steam into a hydrocarbon effluent from a hydrocarbon cracking furnace to reduce the coke material from forming on a TLE exchanger tubesheet at the outlet of the hydrocarbon cracking furnace.
Ethylene is produced by cracking a hydrocarbon feed to produce a hydrocarbon effluent comprising ethylene and numerous other products such as, for example, propylene, butadiene, and benzene. The hydrocarbon cracking is conducted at extreme temperatures, and the hydrocarbon effluent produced then flows from the hydrocarbon cracking heater to the TLE to be cooled. In addition to producing ethylene and other products, a coke material is also produced. The coke material can adhere to a TLE exchanger tubesheet, and eventually will require that the hydrocarbon cracking furnace be shut down in order to mechanically clean the TLE exchanger tubesheet. The adhesion of the coke material is partially because the hydrocarbon effluent velocity is lower on the outer edges of the TLE cone than in the center. Therefore, the reduction in velocity can cause be hydrocarbon effluent to swirl or form eddies, thereby causing the hydrocarbon effluent to have a higher residence time. Generally, when the TLE exchanger is removed for cleaning, up to 20% of the TLE exchanger tubesheet is covered with coke material thus restricting heat transfer and thereby reducing the efficiency of the hydrocarbon cracking furnace.
An inventive solution has been discovered to substantially reduce the coke material from forming on the TLE tubesheet.
It is an object of this invention to provide a method for reducing formation of a coke material on a TLE exchanger tubesheet of a hydrocarbon cracking furnace.
It is another object of this invention to provide an apparatus for injecting steam to reduce the formation of coke material on a TLE exchanger tubesheet of a hydrocarbon cracking furnace.
In accordance with this invention, an apparatus to inject steam into a hydrocarbon effluent passing through the TLE cone of a hydrocarbon cracking furnace is provided. The apparatus comprises:
(a) at least one injection probe, which is connected at an angle in a range of about 30 to about 60 degrees to the TLE cone; and
(b) a distribution nozzle, which is connected to the end of said injection probe, wherein the injection probe and distribution nozzle protrude into the TLE cone by a distance in the range of about 1% to about 10% of the radius of the TLE cone.
In further accordance with this invention, a method to inject steam into a TLE cone of a hydrocarbon cracking furnace to reduce formation of a coke material on the TLE exchanger tubesheet is also provided. The method comprises:
(a) injecting steam through at least one injection probe wherein the injecting is accomplished by the apparatus described previously.